[SOLVED] Question about wiring a 2.1 speaker setup

[Shahmatt]

Dear all, will what is in the below image work?

I want to DIY a 2.1 speaker setup by connecting to a 3.5mm adapter in the way shown. Hope to plug it directly into a PC without need for amp. The speakers are resonance speakers like the Dayton or Aiyima.

I am mainly concerned about impedance. The left and right channels are 8Ohms, but subwoofer (Wharfedale S8E) is 20,000Ohms.

From what little I have read about calculating resistance in parallel, the effective impedance at input would be around 3.99 Ohms. Please correct me if I am wrong. Would there be a chance of damaging the subwoofer?

 

[jay32267]

The effective impedance on each channel is going to be almost 8 ohms.

20,000 ohms is going to have very little effect on the calculation.

The subwoofer appears to be designed for signal level signals (due to it being 20,000 ohms and probably powered) NOT speaker level signals....so I wouldn't connect to it.
The voltages may be too high.

 

[kanewolf]

No. Output from a PC can't directly drive a speaker. You need an amplifier between the PC and 8 ohm speakers.

 

[Shahmatt]

No. Output from a PC can't directly drive a speaker. You need an amplifier between the PC and 8 ohm speakers.

Please correct me if I'm wrong, but I assumed that the lower the impedance the better the ability of the PC to drive the speaker. For example plug-in earphones have low impedance of around 32 Ohms which allows the PC to power it without need for an amp.

For my speakers the impedance is really low, 8 Ohms per unit, which would mean that the PC could overpower it. But I also understand that modern motherboards come with some ability to detect the impedance of the audio device and adjust accordingly.

All of the above ignores the subwoofer. For the sub the electrical output from the source would be insufficient for it to detect, so I suspect I would need an amp between the sub and the PC output.

 

[kanewolf]

Please correct me if I'm wrong, but I assumed that the lower the impedance the better the ability of the PC to drive the speaker. For example plug-in earphones have low impedance of around 32 Ohms which allows the PC to power it without need for an amp.

For my speakers the impedance is really low, 8 Ohms per unit, which would mean that the PC could overpower it. But I also understand that modern motherboards come with some ability to detect the impedance of the audio device and adjust accordingly.

All of the above ignores the subwoofer. For the sub the electrical output from the source would be insufficient for it to detect, so I suspect I would need an amp between the sub and the PC output.

Headphones don't have to generate much sound to seem loud. Speakers have to be much louder. If you put your ear next to the speaker you might hear something. Three feet away, not much.

 

[Shahmatt]

Headphones don't have to generate much sound to seem loud. Speakers have to be much louder. If you put your ear next to the speaker you might hear something. Three feet away, not much.

Thanks

 

[hang-the-9]

Please correct me if I'm wrong, but I assumed that the lower the impedance the better the ability of the PC to drive the speaker. For example plug-in earphones have low impedance of around 32 Ohms which allows the PC to power it without need for an amp.

For my speakers the impedance is really low, 8 Ohms per unit, which would mean that the PC could overpower it. But I also understand that modern motherboards come with some ability to detect the impedance of the audio device and adjust accordingly.

All of the above ignores the subwoofer. For the sub the electrical output from the source would be insufficient for it to detect, so I suspect I would need an amp between the sub and the PC output.

You need to look at the power requirements for the speakers not the ohm rating. Read the second page here https://www.ranecommercial.com/legacy/pdf/old/note100.pdf

If you headphones that are harder to drive, you may need 1/2 a watt to power them to loudness levels too much for most people to listen to, for decent speakers to get to the same volume level you would need 50 watts to get them decently loud without distortion. Many sub amps are in the hundreds of watts.

 

[Shahmatt]

You need to look at the power requirements for the speakers not the ohm rating. Read the second page here https://www.ranecommercial.com/legacy/pdf/old/note100.pdf

If you headphones that are harder to drive, you may need 1/2 a watt to power them to loudness levels too much for most people to listen to, for decent speakers to get to the same volume level you would need 50 watts to get them decently loud without distortion. Many sub amps are in the hundreds of watts.

Thanks. That makes sense.

I've gone ahead and ordered an amp to make this work.